…items containing all the words making up the string:psychological experiments

The search is case-insensitive and diacritics are being added (if necessary). The search supports conjugations and inflections. Example: Searching for Czech diplomova prace also returns the results containing V diplomové práci.

…items containing the exact phrase (the search string as it has been entered):"psychological experiments"

Even if quotation marks are not used, the search engine prioritizes the results which contain the strings most similar to the search one. However, using the quotation marks, you make it clear you are searching for the exact phrase (no diacritics are being added and no inflections are being taken into account).

…items not containing a certain word:experiments -psychological

A dash causes the search engine to return the results not containing the word following it. However, if a hyphen is used instead, the search engine works the same way like it does in the exact phrase searches except that diacritics are being added (if necessary) and inflections are being taken into account. Examples: e-learning or Frýdek-Místek.